function h = logdecimark(x,y,n_mark,marker,linestyles)
semilogy(x,y,'-', linestyles{:}); hold on
n = floor(length(y) / n_mark);
h = semilogy(x(1:n:end), y(1:n:end), marker, linestyles{:});
%length(x(1:n:end))
end
